Released a little over a month ago, Microsoft's new Edge browser has gotten a set of critical security patches.

As part of its monthly round of security fixes, colloquially known as Patch Tuesday, Microsoft released a critical bulletin, MS15-095, with four patches covering vulnerabilities in the Windows 10-only Edge browser.

Overall this month, Microsoft issued 12 bulletins covering 56 vulnerabilities. Five bulletins were deemed as critical, meaning they should be addressed as soon as possible.

Microsoft built Edge as the next generation browser for Windows, one designed to replace Internet Explorer over time.

All the Edge vulnerabilities Microsoft disclosed this month were also found in Internet Explorer, which was covered by MS15-094, pointed out Wolfgang Kandek, chief technology officer for IT security firm Qualys.

"Someone could attack you, whether you have either Internet Explorer or Edge, using a specially crafted Web page," Kandek said.

The duplicates show the code overlap between Edge and IE, indicating that the engineering team developing Edge used at least part of the code base for IE, Kandek said.

But the fact that Edge had fewer vulnerabilities this month than IE, which had 17, shows that Microsoft's engineering effort in building a more secure browser seems to be paying off, Kandek said.

It also shows how difficult it is to write software that is error-free and immune to attackers, he said.

Because Windows 10 hasn't been widely installed in the enterprise yet, reviewing the Edge bulletin may not be the top priority on administrators' to-do lists.

Instead, the bulletins that they should take a look at first are MS15-097 and MS15-099, which describes a number of critical vulnerabilities found in Office 2007 and 2010, advised Amol Sarwate, Qualys director of engineering.

"There are already attacks going on in the wild" that use these vulnerabilities, Sarwate said. Many are remote code execution vulnerabilities, meaning the user only needs to open a maliciously-crafted Excel or Word document, and the code within can execute actions without the user's knowledge.

Those shops running Microsoft Exchange and Active Directory should also take a close look at MS15-096 and MS15-103, covering Active Directory and Microsoft Exchange, respectively.

The Exchange vulnerability could allow a malicious attacker to gain entry to a user's files through the Outlook Web Access (OWA) client.

The Active Directory flaw makes the software vulnerable to a denial of service (DoS) attacks.

Active Directory is typically a critical application for businesses. It keeps track of all the user accounts, and it is not usually exposed to the Internet. But the administrator still should remain diligent in keeping it patched.

"If someone breaks into your network, Active Directory may be the first thing they will try to attack," Sarwate said.

Thus far this year, Microsoft has issued 105 bulletins, and Qualys estimates that number to hit 145 by the end of the year. This is up from years past. In 2014, Microsoft issued 106 bulletins and 100 in 2011. (Those issues that Microsoft finds internally are typically not publicized and instead are patched with routine updates before attackers find out about them.)

"I don't think software is becoming any more vulnerable," Kandek said. Rather a rising number of vulnerabilities stems from more third party researchers and attackers finding problems, coupled with the growing numbers of different products, versions and platforms that products run on.

"It's a good indicator for how important security is becoming," Kandek said.

(Correction: The headline as well as the first and second sentences of this article have been corrected since the story was first posted. The changes in the headline and first sentence are intended to clarify that the security bulletin this month was not the first to issue a critical patch for the Edge browser. The change in the second sentence corrects the number of the relevant security bulletin to MS15-095.)